1. Field of the Invention:
The present invention relates to a method and an apparatus for sterilizing bacteria adhered to a surface of a hand piece to be used by a dentist for treating a patient and to an inner surface of an air communication bore therein and bacteria adhered to other objects to be sterilized by means of ozone gas.
2. Description of the Prior Art:
Heretofore, in a sterilizing apparatus for such type of objects, generally sterilization has been carried out through high-temperature heating with steam under high pressure by use of an autoclave. However, since the hand piece for a dentist is composed of precise mechanical parts such as a chuck for mounting and dismounting a small drill, an air turbine for rotating this chuck at a high speed, a device for cooling the tip end of the drill and the like, there is a fear that the precision may be possibly lost by distortion occurring upon high-temperature heating. Consequently, disinfection and sterilization cannot be carried out sufficiently, and it is surmised that a hygienically serious problem may be caused.
Furthermore, a time of about 15 minutes for heating an object to a temperature that is necessary for sterilization (about 130.degree. C.), a time of about 20 minutes for sterilizing perfectly at that temperature and a time of about 10 minutes for cooling the object, that is, a total time of at least about 45 minutes was necessitated. Hence quick sterilization of a hand piece could not be achieved, and this was quite inconvenient.
Besides the above-mentioned sterilizing apparatus, among the sterilizing apparatuses for the above-described type of objects an apparatus employing ethylene oxide gas is also known, but in this case also, a sterilizing time of at least 50 minutes and, in addition, repeated pressurizing and depressurizing operations for that gas were necessitated. Moreover, there was the shortcoming that ethylene oxide gas which is poisonous and carcinogenic might remain on a hand piece.
Though it can be conceived to carry out sterilization by use of high-concentration ozone gas having a strong sterilizing power and no residual poisonousness in order to avoid the above-mentioned problems, in many cases a hand piece just after treatment of a patient would have its surface wetted and coated with a water film, and so, even if the hand piece under such condition is placed in ozone gas within a sterilizing chamber, the ozone gas would not fully reach bacteria in the water film and perfect sterilization was difficult.
In addition, in the case of certain ones of the bacteria which can be hard to sterilize if the bacteria adhered to the surface of the hand piece are placed under a condition at a temperature lower than a room temperature or held in a dried condition, especially in the case of hey bacillus (Bacillus subtilis), since in their spore a cell membrane forming an outer wall of protoplasm maintains a dense shell structure, ozone gas is intercepted by the shell and cannot penetrate through the shell and reach the protoplasm therein. Therefore, it becomes very difficult to sterilize the bacteria. Furthermore, although it is relatively easy to sterilize a surface of a hand piece because it can be easily exposed to ozone gas, since an inner surface of an air communicating bore in a hand piece can be only partially exposed to ozone gas, it is practically very difficult to sterilize the inner surface.